Jekyll does not automatically generates titles from filename

As you can see in this test page (whose source code is here), all of my blog posts and notes (in my _notes collection) do not have any automatically-generated title from filename (except in cases where I explicitly declare the title: entry in the page front matter), as it should happen, instead. This is my _config.yml

Did I configure something wrong?
Is this a bug or am I missing something?

Thanks a lot!


Apparently, I am going crazy. Everything seems to be working, now. Sorry.